The effect of oral administration of various antigens on the ocular immune response has been tested in the animal model for a severe intraocular inflammatory disease, experimental autoimmune uveioretinitis, which is induced by both retinal S-antigen (S-Ag) and interphotoreceptor retinoid-binding protein (IRBP). Oral tolerance could be induced by repeatedly feeding rats S-Ag. A putative suppressor cell that was CD8 positive could be isolated from the spleen of such animals and transferred to other animals to induce a similar toleragenic effect. In addition, the role of the spleen was confirmed in ongoing animal experiments. A randomized, masked trial to evaluate the usefulness of S-Ag feeding in patients with intraocular inflammatory diseases has been put together. A pilot study performed in two patients showed the induction of such tolerance.